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  • 1.
    Acaralp, Damla
    Södertörn University, Teacher Education.
    Hållbar utveckling i undervisningen: En kvalitativ studie om lärare och lärarstudenters syn på hållbar utveckling i undervisningen2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The issue for this study is how teachers and teacher students understand the concept of sustainable development and work and want to work with sustainable development in their education. The aim is to provide knowledge that can lead to a better implementation of sustainable development in education. The study has a phenomenological perspective and is based on the concept of sustainable development and theories of education for sustainable development. The study consists of interviews with four teachers who act as primary teachers and four teacher students who study on the last semester of their education. The study shows that all respondents think that sustainable development is a concept that is difficult to interpret and that they have a distorted interpretation of the concept. All are focusing on environmental protection and overlook economic and social development. That is particularly apparent in their examples of how sustainable development should be implemented in teaching. The study also shows that the teacher students have a more complete picture of the concept of sustainable development and, unlike the teachers, explicitly states that sustainable development should permeate the entire teaching.

  • 2.
    Ahlbäck, Marcus
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Förnybara energikällor i media2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    To combat the rising global temperature Sweden have signed the Paris Agreement to limit the release of CO2 and keep the temperature to a minimum increase of 1,5 degrees. A transformation of today’s energy system towards renewable energy is paramount to this endeavour, which in part relies on public acceptance where media plays an important role inshaping public acceptance. This study aims to map acceptance of renewable energy sources and draws on framing theory, which states that the media focuses attention on certain events and gives information meaning, in a sense how something is presented to the audience influences their choices in how to process said information. As this is a qualitative study, 49 articles about bio-, geothermal, solar, water and wind energy from Sweden’s four major newspapers, Aftonbladet, Dagens Nyheter, Expressen and Svenska Dagbladet, have been gathered from the Svenska dagstidningar database and examined through frame analysis. Media framing contributing to public acceptance was bio- and solar energy while water subtracted from it. Wind energy were both contributing and subtracting from acceptance while geothermal lacked articles entirely, prohibiting it from entering public discourse altogether. Meanwhile the biggest deciding factor towards framing acceptance for renewable energy depended largely on the newspaper.

  • 3.
    Akrawi, Narin
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies.
    Ciechowicz, Michelle
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies.
    Fotbollsturism: En studie om fotbollsturisters upplevelse och tillfredställelse2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This is a study made by two students for their bachelor theses in Tourism at Södertörn University, Sweden. The study investigates weather the theoretical characteristic features of a sport tourist is inconsistent with reality. The study also investigates factors that sport tourist consider important during a football trip to achieve a satisfying experience. By identifying specific element of the phenomenon increase knowledge and development of sport tourism. The method chosen for the study was qualitative interviews which where performed with twenty respondents, each respondent travel to Lisbon, Portugal to attend the quarter- finals of Champions League between SL Benfica and FC Bayer München, 13 April 2016. The interview material was interpreted and later merges with previous research and theories in order to investigate and identify the phenomenon. The result of the study showed that the theoretical and previous research that have been presented on characteristic features of a sport tourist do not or partly match the respondents in this study. This study also showed that factors that sport tourist consider important as e.g. good seats, security, transport, good company, good atmosphere, other supporters and supporting their favourite football team, are the factors that contribute and makes a satisfying, memorable and positive experience trip.

  • 4.
    Aldén, Nina
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies.
    Is A Holistic Approach Relevant for Non-Governmental Organizations’ Agricultural Extension Strategies?: Case Studies from Tanzania2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Agricultural extension can play a major part in the development and adoption of sustainable agriculture practices. Local NGOs have a unique opportunity to serve as extension agents due to their acceptance and close relationship in communities. The paper argues that agricultural extension needs to adopt a holistic approach to the communities’ development to achieve a lasting and sustainable agriculture. This study examines four NGOs in Tanzania to see 1) how they provide extension services; 2) if they have a holistic approach; and 3) if the holistic approach is a conscious strategy. The findings show that a mixture of extension methods is commonly used by all four of the NGOs. More over the NGOs offer a wide variety of projects, which focus on different issues. This results in a holistic approach, even though this probably is rather a result of funding practices than a conscious extension strategy.

  • 5.
    Aliyu, Habibu
    et al.
    Centre for Microbial Ecology and Genomics, University of Pretoria, Pretoria, South Africa.
    De Maayer, Pieter
    School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, South Africa.
    Sjöling, Sara
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Cowan, Donald A.
    Centre for Microbial Ecology and Genomics, University of Pretoria, Pretoria, South Africa.
    Metagenomic Analysis of Low-Temperature Environments2017In: Psychrophiles: From Biodiversity to Biotechnology / [ed] Rosa Margesin, Cham: Springer, 2017, p. 389-421Chapter in book (Refereed)
    Abstract [en]

    The Earth’s permanently cold biosphere is known to harbour abundant microbial biomass and represents a rich resource for the discovery of novel cold-adapted microorganisms, many of which form part of the ‘microbial dark matter’ which cannot be analysed using traditional culture-dependent approaches. The recent development of metagenomics and related multi-omics strategies has provided a means by which entire microbial communities can be studied directly, without the prerequisite of culturing. The advancement of the ‘omic’ methods is directly linked to recent progress in high-throughput sequencing, robust data processing capabilities and the application of cutting-edge analytical tools for high-throughput detection of biomolecules. The combined application of these tools and strategies has provided an unprecedented access to the structure and potential function of microbial communities in cold environments, providing increasingly comprehensive insights into the taxonomic richness and functional capacity of the indigenous microorganisms. Applications of ‘omic’ strategies have enhanced our understanding of psychrophilic adaptation mechanisms, revealing the versatility and adaptability of life in the ‘cryosphere’. In addition to the predicted roles of psychrophiles in biogeochemical cycling, recent multi-omic studies have further emphasised the importance of the ‘cryosphere’ in influencing global atmospheric conditions. Finally, metagenomic bioprospecting of cold environments has yielded a variety of novel bioactive molecules including novel ‘psychrozymes’, with a wide range of potential industrial and biotechnological applications. Here, we have provided an overview of recent developments in metagenomic technologies and their application in the study of the cold biosphere.

  • 6.
    Andersson, Ingela
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Stockholm University, Department of Physical Geography and Quarternary Geology.
    Jarsjö, Jerker
    Stockholm University, Department of Physical Geography and Quarternary Geology.
    Petersson, Mona
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Geography. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Saving the Baltic Sea, the Inland Waters of Its Drainage Basin, or Both? Spatial Perspectives on Reducing P-Loads in Eastern Sweden2014In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 43, no 7, p. 914-925Article in journal (Refereed)
    Abstract [en]

    Nutrient loads from inland sources to the Baltic Sea and adjacent inland waters need to be reduced in order to prevent eutrophication and meet requirements of the European Water Framework Directive (WFD) and the Baltic Sea Action Plan (BSAP). We here investigate the spatial implications of using different possible criteria for reducing water-borne phosphorous (P) loads in the Northern Baltic Sea River Basin District (NBS-RBD) in Sweden. Results show that most catchments that have a high degree of internal eutrophication do not express high export of P from their outlets. Furthermore, due to lake retention, lake catchments with high P-loads per agricultural area (which is potentially of concern for the WFD) did not considerably contribute to the P-loading of the Baltic Sea. Spatially uniform water quality goals may, therefore, not be effective in NBS-RBD, emphasizing more generally the need for regional adaptation of WFD and BSAP-related goals.

  • 7.
    Andersson, Ingela
    et al.
    Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Geography. Stockholm University, Department of Physical Geography and Quarternary Geology.
    Petersson, Mona
    Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Geography.
    Jarsjö, Jerker
    Stockholm University, Department of Physical Geography and Quarternary Geology.
    Impact of the European Water Framework Directive on local-level water management: Case study Oxunda Catchment, Sweden2012In: Land use policy, ISSN 0264-8377, E-ISSN 1873-5754, Vol. 29, no 1, p. 73-82Article in journal (Refereed)
    Abstract [en]

    The Water Framework Directive (WFD) of the European Union provides a common framework for water policy that focuses on holistic and integrated water management in river basins. In many member states, implementation of the WFD has shifted the main responsibility for local water issues from the municipal level to the regional or supra-regional levels. In this study, we investigated how the implementation of the WFD has influenced local-level water management including the interpretation of the new environmental quality standards. Specifically, we considered Sweden, which has traditionally had relatively strong governance at the municipal level. Because a sufficient amount of time has now passed for evaluation of WFD-related effects on operational water handling, we interviewed individuals directly involved in water planning and land use planning at the municipal level in one sub catchment in the Northern Baltic Sea River Basin District of Sweden, as well as representatives for superior levels and associations. Despite divergent views regarding the priority of water issues in physical planning among the local-level planners interviewed, they had all participated in successful inter-municipal pre-WFD collaboration projects. Although such collaborations could help increase the understanding and acceptance of WFD-related goals and costs, as well as facilitate conflict solving, as shown in the Oxunda Catchment, they have not gained much attention in the WFD implementation process. Additionally, physical planners have generally been reluctant to accept new environmental quality standards resulting from WFD implementation, in part because they lack precise definitions, but also because they could challenge the municipal routine of weighing various objectives against each other. Furthermore, despite WFD-related increases in ambition levels, lack of resource improvements at the municipal level were identified as potential problems by local environmental planners.

  • 8.
    Andersson, Pernilla
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Södertörn University, Teacher Education.
    Business as un-usual through dislocatory moments – change for sustainability and scope for subjectivity in classroom practice2018In: Environmental Education Research, ISSN 1350-4622, E-ISSN 1469-5871, Vol. 24, no 5, p. 648-662Article in journal (Refereed)
    Abstract [en]

    This paper makes a contribution to the debate that has been described as a tension between instrumental and emancipatory educational objectives in environment and sustainability education. The contribution involves a methodological approach (introd-) using the concept ‘dislocatory moments’, to identify and analyse moments in classroom practice that address educational objectives relating to ‘change for sustainability’ and ‘thinking and acting independently’. A case of business education, when ‘sustainable development’ is integrated in a series of lessons, is used to exemplify the approach involving analysis of the emergence and closure of a dislocatory moment and the change of logics that occur. The illustrative case shows how room for subjectivity and change can be intertwined in educational practice. It is suggested that the methodological approach could be used in empirical research of classroom practice to further knowledge about the kind of situations that contribute to ‘business as un-usual’ without compromising emancipatory education ideals.

  • 9.
    Andersson, Pernilla
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Södertörn University, Teacher Education.
    Equipped for responsibility: A case of business education for sustainabilityManuscript (preprint) (Other academic)
    Abstract [en]

    This paper presents a study of the roles of a business person articulated byteachers in the classroom when the concept of sustainable development is incorporated into the subject of business economics. The empirical material, consisting of video recorded observations in five teachers’ classrooms, was collected two years after the inclusion of the concept in theupper secondary school syllabus in Sweden. The concept of logics developed within a discourse theoretical framework is used to analyse the meaning of ‘doing business sustainably’ as depicted by teachers in classroom practice. The paper illustrates that different rules and conditions for doing business are foregrounded in classroom practice by distinguishing between the logics of self-interest, conscious consumers and stakeholders’ interests. Each logic positions a business person differently. These positions are analysed using a typology of responsibility. The conclusion is that students could become unequipped, ill-equipped or better equipped to address uncertain and complex sustainability issues depending on how sustainable development is integrated into the business curriculum.

  • 10.
    Andersson, Pernilla
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Södertörn University, Teacher Education.
    The Responsible Business Person: Studies of business education for sustainability2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Calls for the inclusion of sustainable development in the business curriculum have increased significantly in the wake of the financial crisis and increased concerns around climate change. This has led to the appearance of new initiatives and the development of new teaching approaches. This thesis explores business education at the upper secondary school level in Sweden following the inclusion of the concept of sustainable development in the curriculum. Drawing on poststructuralist discourse theory, the overarching purpose is to identify the roles of a responsible business person that are articulated in business education and to discuss how these roles could enable students to address sustainability issues. The thesis consists of four studies, based on textbook analyses, teacher interviews and classroom observations. Three categories of roles have been identified, implying that a business person is expected to either adapt to, add or create ethical values. These three categories are compared with the roles indicated in the environmental discourses constructed by Dryzek and the responsibility regimes developed by Pellizzoni. Drawing on Dryzek’s and Pellizzoni’s reasoning about which qualities are important for addressing sustainability issues, it is concluded that the roles identified in the studies could mean that students are unequipped (the adapting role), ill-equipped (the adding role) or better equipped (the creating role) to address uncertain and complex sustainability issues. The articles include empirical examples that illustrate how and in which situations specific roles are articulated, privileged or taken up. The examples also indicate how the scope for business students’ subjectivities are facilitated or hampered. It is suggested that the illustrative empirical examples could be used for critical reflection in order to enhance students’capabilities of addressing uncertain and complex sustainability issues and to improve educational quality in terms of scope for subjectivity.

  • 11.
    Andersson Wargert, Gunnar
    Södertörn University College, School of Life Sciences.
    GIS - A Potential Tool for Development in Babati2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The Geographical Information System (GIS) is a popular tool among landscape plannersas well as administration departments on both local as well as national level. It is asystem that can store and manipulate spatial data and its potential has increased ascomputers have grown to be more and more sophisticated. However the system is notwithout its controversy. Maps and geographical information has been accused of helpinggovernment maintaining its power thus leading to increased surveillance in society. As arespond to this critique Public Participatory Geographical Information System (PPGIS)was developed. PPGIS quickly grew and has been implemented in a wide variety ofprojects. The purpose of this paper is to explore to what extent these aspect plays a partin the implementation of GIS and PPGIS in Babati, Tanzania. More specifically, couldBabati handle a complex and resource demanding system such as GIS? To clarify howGIS could play a beneficial part in Babati development, a high rate in population growthas well as department clashes will be illustrating examples. In Babati there have beenrepeatedly conflicts between the water department and the Babati town council and someof them are directly related to communication issues. A hypothesis suggests that GIS haspotential in creating cohesion and a communication tool operating through geographicaldata. In generally results show that GIS could lead to better development, but at the sametime risk alienating people from participating in the decision making. Consequently ifGIS would be effective in Babati, it would have to be adapted to the region it is appliedto, funded on the towns’ resources and knowledge. If it does not it risks failing in thelong term as well as not living up to expected standard. PPGIS could possibly avoid someof the issues that might appear when implementing GIS but it is unlikely that it has all theanswers. PPGIS can improve the situation for marginalized people but a societyundemocratic issue is more likely to stem from several of different aspects.

  • 12.
    Andrén, Elinor
    Stockholm University.
    Changes in the composition of the diatom flora during the last century indicate increased eutrophication of the oder estuary, south-western Baltic Sea1999In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 48, p. 665-676Article in journal (Refereed)
    Abstract [en]

    Four short sediment cores from the Oder estuary, south-western Baltic Sea, were studied with respect to their siliceous microfossil and organic carbon content. The sediments were dated by Pb-210. The objective was to detect and date changes in the composition of the diatom flora and link these changes to increased human impact in the drainage area during recent centuries. Two of the cores showed an unperturbed sedimentary sequence representing a complete historical record. A change in the composition of the diatom assemblages attributable to anthropogenic factors was recorded. This was dated to about 1900 in the Oderhaff. The change consisted of an increase in species that thrive in eutrophic waters and those indicating increased salinity or the availability of inorganic nutrients.

  • 13.
    Andrén, Elinor
    Södertörn University College, School of Chemistry, Biology, Geography and Environmental Science.
    Naturliga halter – vad är det?: Historiska arkiv ger referensvärden.2005In: Miljötillståndet i egentliga Östersjön: Rapport 2005, Stockholm: Stockholms marina forskningscentrum , 2005, p. 50-62Chapter in book (Other (popular science, discussion, etc.))
  • 14.
    Andrén, Elinor
    Södertörn University College, School of Life Sciences.
    Reflektioner från BERINGIA 2005: en svensk polarforskningsexpedition till Kamtjatka2008In: Ymer, ISSN 0044-0477, p. 113-151Article in journal (Other academic)
  • 15.
    Andrén, Elinor
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Andrén, Thomas
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Syrefria bottnar - orsakade av klimat, människa eller både och?2014In: Havsutsikt, ISSN 1104-0513, no 2, p. 12-14Article in journal (Other (popular science, discussion, etc.))
  • 16.
    Andrén, Elinor
    et al.
    Stockholm University.
    Andrén, Thomas
    Stockholm University.
    Kunzendorf, Helmar
    Risø National Laboratory.
    Holocene history of the Baltic Sea as a background for assessing records of human impact in the sediments of the Gotland Basin2000In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 10, p. 687-702Article in journal (Refereed)
    Abstract [en]

    Sediment cores from the Gotland Basin were studied for their siliceous microfossil assemblages and organic carbon content to compare recent environmental changes in the Baltic Sea with its natural long-term history. Age models were constructed using Pb-210, Cs-137 and corrected and calibrated C-14 dates. The transgression that marks the onset of the Ancylus Lake stage is recorded in the sediments as a small increase in organic carbon coinciding with a peak in diatom abundance and increased diatom diversity. A minor occurrence of brackish-freshwater diatoms is recorded in the Ancylus Lake c. 9950-9750 cal. yr BP (c. 8900-8800 C-14 yr BP), correlating with the onset of the Initial Litorina Sea in the Bornholm Basin. A high-productivity event is recorded in the end of the Post-Litorina Sea and corresponds to the Mediaeval warm event. An alteration in the diatom assemblage contemporaneous with a decrease in organic carbon, interpreted as representing a deterioration in the climate, correlates with the start of the ‘Little Ice Age’ about 850-700 cal. yr BP. A change dated to ad 1950-1960 is probably an effect of increased nutrient availability in the open Baltic Sea. This effect of eutrophication was probably caused by increased discharge of nutrients deriving from fertilizers, as the responding diatom species partly indicate a cold climate rather than a warm one, as would have been expected if this had been only a response to the warmer climate documented during the last 100 years or so.

  • 17.
    Andrén, Elinor
    et al.
    Stockholm University.
    Andrén, Thomas
    Stockholm University.
    Sohlenius, Gustav
    Swedish University of Agriculture.
    The Holocene history of the southwestern Baltic Sea as reflected in a sediment core from the Bornholm Basin2000In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 29, p. 233-250Article in journal (Refereed)
    Abstract [en]

    A study of changes in siliceous microfossil assemblages and chemical analyses in a well-dated offshore sediment core from the Bornholm Basin, southwestern Baltic Sea, is carried out with the objective of increasing knowledge of the Holocene history of the area. The core covers about 11 300 calendar years from the brackish phase of the Yoldia Sea stage to the present. The first weak marine influence in the Ancylus Lake stage is recorded about 10 100 cal. yr BP (c. 8900 C-14 BP), indicating a complex transition to the Litorina Sea with different phases of brackish-water inflow. The lithology, organic carbon content and C/N and C/S ratios indicate no major changes in the sedimentary environment during the Litorina-Post-Litorina Sea stages. A high productivity event recorded in the Post-Litorina Sea stage around 950 cal. yr BP correlates with the Medieval warm event. A biostratigraphical change indicating a colder climate is recorded in the sediment at about 800 cal. yr BP, which might mark the beginning of the Little Ice Age.

  • 18.
    Andrén, Elinor
    et al.
    Södertörn University College, School of Life Sciences.
    Clarke, Annemarie
    Telford, Richard
    Weckström, Kaarina
    Vilbaste, Sirje
    Aigars, Juris
    Conley, Daniel
    Johnsen, Torbjørn
    Juggins, Steve
    Korhola, Atte
    Defining Reference Conditions for Coastal Areas in the Baltic Sea2007Report (Other academic)
    Abstract [en]

    The overall aim of DEFINE is to provide a methodology to define reference conditions for nutrient concentrations in the coastal zone of the Baltic Sea. This will aid the national authorities that surround the Baltic basin in implementing the EU's Water Framework Directive (WFD) by providing decision-makers with a methodology to assess reference conditions and the degree of past and present departure from this state, such that appropriate policy and management measures can be taken at national and European levels. DEFINE adopts a palaeoecological approach grounded on diatom-based transfer functions, which can then be applied to define background total nitrogen (TN) concentrations in estuaries and coastal areas over the entire Baltic Sea. All transfer functions and necessary supporting documentation will be publicly available as a coherent management tool and accessible via the MOLTEN/DEFINE web page (http://craticula.ncl.ac.uk/Molten/jsp/).

  • 19.
    Andrén, Elinor
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Klimaschewski, Andrea
    Queen's University Belfast, UK.
    Self, Angela E.
    The Natural History Museum, London, UK.
    St. Amour, Natalie
    University of Western Ontario, London, Ontario, Canada.
    Andreev, Andrei A.
    University of Cologne, Cologne, Germany.
    Bennett, Keith D.
    Kazan Federal University, Kazan, Russia / Uppsala University.
    Conley, Daniel J.
    Lund University, Lund, Sweden.
    Edwards, Thomas W.D.
    University of Waterloo, Ontario, Canada.
    Solovieva, Nadia
    Kazan Federal University, Kazan, Russia / University College London, UK.
    Hammarlund, Dan
    Lund University, Lund, Sweden.
    Holocene climate and environmental change in north-eastern Kamchatka (Russian Far East), inferred from a multi-proxy study of lake sediments2015In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 134, p. 41-54Article in journal (Refereed)
    Abstract [en]

    A sediment record from a small lake in the north-eastern part of the Kamchatka Peninsula has been investigated in a multi-proxy study to gain knowledge of Holocene climatic and environmental change. Pollen, diatoms, chironomids and selected geochemical parameters were analysed and the sediment record was dated with radiocarbon. The study shows Holocene changes in the terrestrial vegetation as well as responses of the lake ecosystem to catchment maturity and multiple stressors, such as climate change and volcanic eruptions. Climate change is the major driving force resulting in the recorded environmental changes in the lake, although recurrent tephra deposition events also contributed. The sediment record has an age at the base of about 10,000 cal yrs BP, and during the first 400 years the climate was cold and the lake exhibited extensive ice-cover during winter and relatively low primary production. Soils in the catchment were poor with shrub alder and birches dominatingthe vegetation surrounding the lake. At about 9600–8900 cal yrs BP the climate was cold and moist, and strong seasonal wind stress resulted in reduced ice-cover and increased primary production. After ca. 8900 cal yrs BP the forest density increased around the lake, runoff decreased in a generally drier climate resulting in decreasedprimary production in the lake until ca. 7000 cal yrs BP. This generally dry climate was interrupted by a brief climatic perturbation, possibly attributed to the 8.2 ka event, indicating increasingly windy conditions with thick snow cover, reduced ice-cover and slightly elevated primary production in the lake. The diatom record shows maximum thermal stratification at ca. 6300–5800 cal yrs BP and indicates together with the geochemical proxies a dry and slightly warmer climate resulting in a high productive lake. The most remarkably change in the catchment vegetation occurred at ca. 4200 cal yrs BP in the form of a conspicuous increase in Siberian dwarf pine (Pinus pumila), indicating a shift to a cooler climate with a thicker and more long-lasting snow cover. Thisvegetational change was accompanied by marked shifts in the diatom and chironomid stratigraphies, which are also indicative of colder climate and more extensive ice-cover.

  • 20. Andrén, Elinor
    et al.
    Shimmield, Graham
    Brand, Timothy
    Environmental changes of the last three centuries indicated by siliceous microfossil records from the southwestern Baltic Sea1999In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 9, p. 25-38Article in journal (Refereed)
    Abstract [en]

    Four short sediment cores from the southwestern Baltic Sea were analysed with respect to their content of siliceous microfossils. The aim was to detect and date changes in the composition of the diatom flora and to link these changes to variations in the anthropogenic load of nutrients during the last century. The study shows that the most significant change in the diatom assemblages occurred 130-140 years ago. The change is recorded in the sediments as a shift from periphytic diatom taxa to a predominance of planktonic taxa. This indicates that the photic layer has decreased in depth, probably due to eutrophication of the Baltic Sea, which consequently began to affect the area investigated approximately AD 1850. To support the results of a changing ratio of periphytic to planktonic diatoms, diatom accumulation rates were calculated In general, the diatom accumulation rate data show a decrease in the periphytic accumulation rates and an increase in the planktonic accumulation rates towards the sediment surface. Some indications of a colder climate are recorded in the sediments approximately 230 years ago. These results are in accordance with the record of maximum extent of sea ice in the same area and are suggested to represent a late stage in the ‘Little Ice Age’.

  • 21.
    Andrén, Elinor
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Telford, Richard J.
    University of Bergen.
    Jonsson, Per
    Stockholm University.
    Reconstructing the history of eutrophication and quantifying total nitrogen reference conditions in Bothnian Sea coastal waters2017In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 198, p. 320-328Article in journal (Refereed)
    Abstract [en]

    Reference total nitrogen (TN) concentrations for the Gårdsfjärden estuary in the central Bothnian Sea, which receives discharge from an industrial point-source, have been estimated from diatom assemblages using a transfer function. Sedimentological and diatom evidence imply a good ecological status before 1920 with an assemblage dominated by benthic taxa indicating excellent water transparency, high diatom species richness and less organic sedimentation resulting in homogeneous well oxygenated sediments. A change in the diatom assemblage starts between 1920 and 1935 when the species richness declines and the proportion of planktic taxa increases. Increased organic carbon sedimentation after 1920 led to hypoxic bottom waters, and the preservation of laminae in the sediments. The trend in the reconstructed TN-values agrees with the history of the discharge from the mill, reaching maximum impact during the high discharge between 1945 and 1990. The background condition for TN in Gårdsfjärden is 260-300 μg L-1, reconstructed until 1920.

  • 22.
    Andrén, Thomas
    Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Geography.
    Baltic Sea Basin, since the latest deglaciation2012In: Encyclopedia of Lakes and Reservoirs / [ed] Lars Bengtsson, Reginald W. Herschy, Rhodes W. Fairbridge, Dordrecht: Springer Science+Business Media B.V., 2012, p. 95-102Chapter in book (Refereed)
  • 23.
    Andrén, Thomas
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    The Younger Dryas - Pre-boreal transition as recorded in vared glacial clay sequences in the north-western Baltic Proper1996In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 118, p. A79-Article in journal (Refereed)
  • 24.
    Andrén, Thomas
    Stockholm University.
    Till stratigraphy and ice recession in the Bothnian Bay1990Doctoral thesis, monograph (Other academic)
  • 25.
    Andrén, Thomas
    Stockholms universitet.
    Östersjön under åttatusen år: dagens situation är inte ny.2006In: Östersjön: hot och hopp / [ed] Birgitta Johansson, Stockholm: Forskningsrådet Formas, 2006, p. 41-50Chapter in book (Other (popular science, discussion, etc.))
  • 26.
    Andrén, Thomas
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Andrén, Elinor
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Did The Storegga tsunami affect the Baltic Sea?2001In: Baltica: an International Yearbook for Quaternary Geology and Palaeogeography, Coastal Morphology and Shore Processes, Marine Geology and Recent Tectonics of the Baltic Sea Area, ISSN 0067-3064, E-ISSN 1648-858X, Vol. 14, p. 115-123Article in journal (Refereed)
  • 27.
    Andrén, Thomas
    et al.
    Stockholm University.
    Andrén, Elinor
    Södertörn University, School of Life Sciences.
    Berglund, Björn E.
    Lund University.
    Yu, Shi-Yong
    University of Minnesota.
    New insights on the Yoldia Sea low stand in the Blekinge archipelago, southern Baltic Sea2007In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 129, no 4, p. 277-285Article in journal (Refereed)
    Abstract [en]

    One sediment core from the Jarnavik bay in Blekinge archipelago has been investigated for its content of pollen and diatoms and its chemical properties. Two levels were also dated by radiocarbon. Based on the results the sediment sequence analysed has been divided into three environmental units largely corresponding to the lithology of the sequence. A lowermost unit consisting of weakly varved and homogeneous clay was deposited during the end of the brackish phase of the Yoldia Sea at a moderate water depth. On top of this unit a gyttja-clay unit was deposited. The onset of the deposition of this unit has been dated to c. 11 100 cal. yrs. BP. An increasing organic production and increased terrestrial influence is recorded in the chemical data and a very shallow water depth is indicated in the pollen and diatom flora. These results point to conditions in a bay probably isolated from the Yoldia Sea. A local tentative shore displacement curve have been constructed and it is proposed that this unit represents the low stand at c. -18 m during the Yoldia Sea stage in this part of the Baltic Sea basin. The uppermost unit consists of homogeneous clay with a low content of organic carbon. An increasing water depth is indicated by the composition of both pollen and diatoms. The diatom flora also displays an increase in freshwater species. This environmental change was probably the result of a transgression in the beginning of the Ancylus Lake stage.

  • 28.
    Andrén, Thomas
    et al.
    Södertörn University College, School of Life Sciences.
    Andrén, Elinor
    Södertörn University College, School of Life Sciences.
    Nordberg, Kjell
    Omstedt, Anders
    Östersjön förändras ständigt2005In: Upsala nya tidning, ISSN 1104-0173, no 8/6Article in journal (Other (popular science, discussion, etc.))
  • 29.
    Andrén, Thomas
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Andrén, Elinor
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Omstedt, Anders
    Nordberg, Kjell
    Östersjön förändras ständigt2005In: Upsala Nya Tidning, ISSN 1104-0173, p. 3-Article in journal (Other (popular science, discussion, etc.))
  • 30.
    Andrén, Thomas
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Andrén, Elinor
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Zhang, Rui
    Xiamen University, China.
    Baltic Sea Basin Paleoenvironment: paleoenvironmental evolution of the Baltic Sea Basin through the last glacial cycle2014Report (Other academic)
  • 31.
    Andrén, Thomas
    et al.
    Södertörn University, School of Life Sciences, Environmental science.
    Barker Jørgensen, Bo
    Aarhus University, Denmark.
    Cotterill, Carlo
    British Geological Survey, UK.
    Morgan, Sally
    University of Leicester, UK.
    IODP Expedition 347:Paleoenvironmental evolution of the Baltic Sea Basin through the last glacial cycle2012In: ECORD Newsletter, ISSN 2264-1556, no 19, p. 14-15, 23Article in journal (Other academic)
  • 32. Andrén, Thomas
    et al.
    Björck, J
    Johnsen, S
    Correlation of Swedish glacial varves with the Greenland (GRIP) oxygen isotope record1999In: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 14, no 4, p. 361-371Article in journal (Refereed)
    Abstract [en]

    A mean varve thickness curve has been constructed for a part of the Swedish varve chronology from the northwestern Baltic proper. The mean varve thickness curve has been correlated with the delta(18)O record from the GRIP ice-core using the Younger Dryas-Preboreal climate shift. This climate shift was defined by pollen analyses. The Scandinavian ice-sheet responded to a warming at the end of the Younger Dryas, ca. 10 995 to 10 700 clay-varve yr BP. Warming is recorded as a sequence of increasing mean varve thickness and ice-rafted debris suggesting intense calving of the ice front. The Younger Dryas-Preboreal climatic shift is dated to ca. 10 650 clay-varve yr BP, about 40 yr after the final drainage of the Baltic Ice Lake. Both the pollen spectra and a drastic increase in varve thickness reflect this climatic shift. A climate deterioration, correlated with the Preboreal oscillation, is dated to ca. 10 440 to 10 320 clay-varve yr BP and coincides with the brackish water phase of the Yoldia Sea stage. The ages of the climatic oscillations at the Younger Dryas-Preboreal transition show an 875 yr discrepancy compared with the GRIP record, suggesting a large error in the Swedish varve chronology in the part younger than ca. 10 300 clay-varve yr BP.

  • 33.
    Andrén, Thomas
    et al.
    Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Geography.
    Björck, S
    Andrén, Elinor
    Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Geography.
    Conley, D J
    Lambeck, K
    Zillén, L
    The development of the Baltic Sea basin during the last 130 000 years2011In: The Baltic Sea Basin / [ed] Jan Harff, Svante Björck, Peer Hoth, Springer Berlin/Heidelberg, 2011, p. 75-97Chapter in book (Other academic)
  • 34. Andrén, Thomas
    et al.
    Brunnberg, L
    Miller, U
    PROCEEDINGS FROM THE BALTIC-ICE-LAKE-YOLDIA-SEA-SYMPOSIUM, MARCH 1993: PREFACE1995In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 27, p. 3-3Article in journal (Other academic)
  • 35.
    Andrén, Thomas
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Brunnberg, Lars
    Ringberg, Bertil
    The Reactivated Geochronological Institute in Stockholm - The First Clay-varve Database1995In: Journal of European Study Group on Physical, Chemical, Biological and Mathematical Techniques applied on Archaeology (PACT), ISSN 0257-8727, Vol. 50, p. 213-218Article in journal (Refereed)
  • 36.
    Andrén, Thomas
    et al.
    Södertörn University, School of Life Sciences, Environmental science.
    Jørgensen, B. B.
    Aarhus Universit, Denmark.
    Cotterill, C.
    British Geological Survey, UK.
    Baltic Sea Basin Paleoenvironment: paleoenvironmental evolution of the Baltic Sea Basin through the last glacial cycle2012Report (Other academic)
  • 37.
    Andrén, Thomas
    et al.
    Södertörn University, School of Life Sciences.
    Jørgensen, Bo Barker
    Aarhus University, Aarhus, Denmark.
    Cotterill, Carol
    British Geological Survey Murchison House, Edinburgh, UK.
    Baltic Sea Basin Paleoenvironment: Paleoenvironmental evolution of the Baltic Sea Basinthrough the last glacial cycle2012In: IODP Scientific Prospectus 347Article, review/survey (Other academic)
  • 38.
    Andrén, Thomas
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Jørgensen, Bo Barker
    Cotterill, Carol
    Green, Sophie
    IODP expedition 347: Baltic Sea basin paleoenvironment and biosphere2015In: Scientific Drilling, ISSN 1816-8957, E-ISSN 1816-3459, Vol. 20, p. 1-12Article in journal (Refereed)
    Abstract [en]

    The Integrated Ocean Drilling Program (IODP) expedition 347 cored sediments from different settings of the Baltic Sea covering the last glacial–interglacial cycle. The main aim was to study the geological development of the Baltic Sea in relation to the extreme climate variability of the region with changing ice cover and major shifts in temperature, salinity, and biological communities. Using the Greatship Manisha as a European Consortium for Ocean Research Drilling (ECORD) mission-specific platform, we recovered 1.6 km of core from nine sites of which four were additionally cored for microbiology. The sites covered the gateway to the North Sea and Atlantic Ocean, several sub-basins in the southern Baltic Sea, a deep basin in the central Baltic Sea, and a river estuary in the north.

     

    The waxing and waning of the Scandinavian ice sheet has profoundly affected the Baltic Sea sediments. During theWeichselian, progressing glaciers reshaped the submarine landscape and displaced sedimentary deposits from earlier Quaternary time. As the glaciers retreated they left a complex pattern of till, sand, and lacustrine clay, which in the basins has since been covered by a thick deposit of Holocene, organic-rich clay. Due to the stratified water column of the brackish Baltic Sea and the recurrent and widespread anoxia, the deeper basins harbor laminated sediments that provide a unique opportunity for high-resolution chronological studies.

     

    The Baltic Sea is a eutrophic intra-continental sea that is strongly impacted by terrestrial runoff and nutrient fluxes. The Holocene deposits are recorded today to be up to 50m deep and geochemically affected by diagenetic alterations driven by organic matter degradation. Many of the cored sequences were highly supersaturated with respect to methane, which caused strong degassing upon core recovery. The depth distributions of conservative sea water ions still reflected the transition at the end of the last glaciation from fresh-water clays to Holocene brackish mud. High-resolution sampling and analyses of interstitial water chemistry revealed the intensive mineralization and zonation of the predominant biogeochemical processes. Quantification of microbial cells in the sediments yielded some of the highest cell densities yet recorded by scientific drilling.

  • 39.
    Andrén, Thomas
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Jørgensen, Bo Barker
    Cotterill, Carol
    Green, Sophie
    Andrén, Elinor
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Baltic Sea Basin Paleoenvironment: Expedition 347 of the mission-specific drilling platform  from and to Kiel, Germany Sites M0059–M0067  12 September–1 November 20132015Report (Other academic)
  • 40.
    Andrén, Thomas
    et al.
    Södertörn University, School of Life Sciences.
    Jørgensen, Bo Barker
    Aarhus University, Aarhus, Denmark.
    Cotterill, Carol
    ECORD Science Operator, British Geological Survey, Murchison House, Edinburgh, UK.
    Morgan, Sally
    University of Leicester, Leicester, UK.
    IODP Expedition 347: Paleoenvironmental evolution of the Baltic Sea Basin trough the last glacial cycle2012In: ECORD Newsletter, no 19 October, p. 14-15+ s.23Article in journal (Other (popular science, discussion, etc.))
  • 41.
    Andrén, Thomas
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Lindeberg, Greger
    A shallow refraction seismic survey at Björkö eastern Sweden: a pilot study1997In: Environment and Vikings: scientific methods and techniques / [ed] Urve Miller and Helen Clarke, Stockholm: Birka Project, Riksantikvarieämbetet och Statens historiska museer , 1997, p. 175-188Chapter in book (Refereed)
  • 42. Andrén, Thomas
    et al.
    Lindeberg, Greger
    Andrén, Elinor
    Evidence of the final drainage of the Baltic Ice Lake and the brackish phase of the Yoldia Sea in glacial varves from the Baltic Sea2002In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 31, p. 226-238Article in journal (Refereed)
    Abstract [en]

    A clay-varve chronology based on 14 cross-correlated varve graphs from the Baltic Sea and a mean varve thickness curve has been constructed. This chronology is correlated with the Swedish Time Scale and covers the time span 11 530 to 10 250 varve years BP. Two cores have been analysed for grain size, chemistry, content of diatoms and changes in colour by digital colour analysis. The final drainage of the Baltic Ice Lake is dated to c. 10800 varve years BP and registered in the cores analysed as a decrease in the content of clay. This event can be correlated with atmospheric D 14 C content and might have resulted in an increase in these values recorded between 11565 and 11545 years BP. The results of the correlation between the varve chronology from the Baltic Sea, the Greenland GRIP ice core and the atmospheric D 14 C record indicate that c. 760 years are missing in the Swedish Time Scale in the part younger than c. 10 250 varve years BP. A change in colour from a brownish to grey varved glacial clay recorded c. 10 770 varve years BP is found to be the result of oxygen deficiency due to an increase in the rate of sedimentation in the early Preboreal. The first brackish influence is recorded c. 10 540 varve years BP in the northwestern Baltic Sea and some 90 years later in the eastern Gotland Basin.

  • 43.
    Andrén, Thomas
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Risberg, Jan
    Late Quaternary development of the north-western Baltic Proper. An introduction.1994In: Journal of European Study Group on Physical, Chemical, Biological and Mathematical Techniques applied on Archaeology (PACT), ISSN ISSN 0257-8727, Vol. 41, p. 35-43Article in journal (Refereed)
  • 44. Andrén, Thomas
    et al.
    Sohlenius, Gustav
    Clay-varve chronology and magnetic stratigraphy in the nprth-western Baltic Proper1995In: Proceedings of the Third Marine Geological Conference "The Baltic" / [ed] Józef Edward Mojski, Warszawa: Państwowy Inst. Geologiczny , 1995, p. 78-83Conference paper (Refereed)
  • 45. Andrén, Thomas
    et al.
    Sohlenius, Gustav
    Late Quaternary development of the north-western Baltic Proper: Results from the clay-varve investigation1995In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 27, p. 5-10Article in journal (Refereed)
    Abstract [en]

    Within the project "Late Quaternary development of the north-western Baltic Proper" a total of 36 piston core samples have been collected. The results presented in this study are based on analyses of 7 cores with emphasis on the late glacial part of the sequence. The varved glacial clay sequences have been analyzed for calcareous micro-fossils and mineral magnetic properties as well as measurements of clay-varves. The results from these analyses indicate that there is a close correlation between the occurrence of brackish water ostracods and foraminifera and a distinct change in the mineral magnetic parameters. The lithological composition of the clay-varves also differs in this sequence. The duration of this marine phase of the Yoldia Sea stage is 60 to 120 clay-varve years. It is concluded that correlations between the cores can be made using fossil assemblages and mineral magnetic parameters. It has not yet been possible, however, to make any reliable clay-varve connections.

  • 46.
    Andrén, Thomas
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Wannäs, Kjell
    Late Quaternary development of the Bornholm Gatt1988In: Geological Survey of Finland Special Paper, ISSN 0782-8535, Vol. 6, p. 23-30Article in journal (Refereed)
  • 47.
    Asghar, Naveed
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Ticks and Tick-borne Encephalitis Virus: From Nature to Infection2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Vector-borne diseases are an increasing global threat to humans due to climate changes, elevating the risk of infections transmitted by mosquitos, ticks, and other arthropod vectors. Ixodes ricinus, a common tick in Europe, transmits dangerous tick-borne pathogens to humans. Tick-borne encephalitis (TBE) is a vector-borne disease caused by TBE virus (TBEV). Climate change has contributed to increased tick abundance and incidence of tick-borne diseases, and between 10,000 and 15,000 human TBE cases are reported annually in Europe and Asia. TBEV shows a patchy geographical distribution pattern where each patch represents a natural focus. In nature, TBEV is maintained within the tick-rodent enzootic cycle. Co-feeding is the main route for TBEV transmission from infected to uninfected ticks and for maintenance within the natural foci. The increasing number of TBE cases in Scandinavia highlights the importance of characterizing additional TBEV sequences and of identifying novel natural foci, and in this work we sequenced and phylogenetically characterized four TBEV strains: Saringe-2009 (from a blood-fed nymph), JP-296 (from a questing adult male), JP-554 (from a questing adult male), and Mandal-2009 (from a pool of questing nymphs, n = 10). Mandal-2009 represents a TBEV genome from a natural focus in southern Norway. Saringe-2009 is from a natural endemic focus in northern Stockholm, Sweden, and JP-296 and JP-554 originate from a natural focus “Torö” in southern Stockholm. In addition, we have studied the effect of different biotic and abiotic factors on population dynamics of I. ricinus in southern Stockholm and observed significant spatiotemporal variations in tick activity patterns. Seasonal synchrony of immature stages and total tick abundance are important factors for the probability of horizontal transmission of TBEV among co-feeding ticks. We found that the probability of co-occurrence of larvae, nymphs, and female adults was highest during early summer whereas increasing vegetation height and increasing amounts of forest and open water around the study sites had a significant negative effect on co-occurrence of larvae, nymphs, and female adults.

    The proximal part of the 3 ́non-coding region (3 ́NCR) of TBEV contains an internal poly(A) tract, and genomic analysis of Saringe-2009 revealed variability in the poly(A) tract indicating the existence of different variants within the TBEV pool of Saringe-2009. Like other RNA viruses, TBEV exists as swarms of unique variants called quasispecies. Because Saringe-2009 came from an engorged nymph that had been feeding on blood for >60 h, we propose that Saringe-2009 represents a putative shift in the TBEV pool when the virus switches from ectothermic/tick to endothermic/mammalian environments. We investigated the role of poly(A) tract variability in replication and virulence of TBEV by generating two infectious clones of the TBEV strain Toro-2003, one with a short/wild-type (A)3C(A)6 poly(A) tract and one with a long (A)3C(A)38 poly(A) tract. The infectious clone with the long poly(A) tract showed poor replication in cell culture but was more virulent in C57BL/6 mice than the wild-type clone. RNA folding predictions of the TBEV genomes suggested that insertion of a long poly(A) tract abolishes a stem loop structure at the beginning of the 3 ́NCR. Next generation sequencing (NGS) analysis of the TBEV genomes after passaging in cell culture and/or mouse brain revealed molecular determinants and quasispecies structure that might contribute to the observed differences in virulence. Our findings suggest that the long poly(A) tract imparts instability to the TBEV genome resulting in higher quasispecies diversity that in turn contributes to TBEV virulence. Phylogenetic analysis of Saringe-2009, JP-296, JP-554, and Mandal-2009 predicted a strong evolutionary relationship among the four strains. They clustered with Toro-2003, the first TBEV strain from Torö, demonstrating a Scandinavian clade. Except for the proximal part of the 3 ́NCR, TBEV is highly conserved in its genomic structure. Genomic analysis revealed that Mandal-2009 contains a truncated 3 ́NCR similar to the highly virulent strain Hypr, whereas JP-296 and JP-554 have a genomic organization identical to Toro-2003, the prototypic TBEV strain from the same natural focus. NGS revealed significantly higher quasispecies diversity for JP-296 and JP-554 compared to Mandal-2009. In addition, single nucleotide polymerphism (SNP) analysis showed that 40% of the SNPs were common between quasispecies populations of JP-296 and JP-554, indicating the persistence and maintenance of TBEV quasispecies within the natural focus.

    Taken together, these findings indicate the importance of environmental factors for the occurrence pattern of the different life-stages of the tick vector, which are important for the persistence of TBEV in nature. Our findings also show that the selection pressure exerted by specific host also affects the population structure of the TBEV quasispecies. In addition, our results further demonstrate that the evolution of quasispecies has effect on TBEV virulence in mice.

  • 48.
    Asghar, Naveed
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Biology. Örebro universitet.
    Lee, Yi-Ping
    Umeå universitet.
    Nilsson, Emma
    Umeå universitet.
    Lindqvist, Rickard
    Umeå universitet.
    Melik, Wessam
    Örebro universitet.
    Kröger, Andrea
    6Helmholtz Centre for Infection Research, Braunschweig, Germany / University of Magdeburg, Magdenbrug, Germany.
    Överby, Anna K.
    Umeå universitet.
    Johansson, Magnus
    Örebro universitet.
    The role of the poly(A) tract in the replication and virulence of tick-borne encephalitis virus2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, no 6, article id 39265Article in journal (Refereed)
    Abstract [en]

    The tick-borne encephalitis virus (TBEV) is a flavivirus transmitted to humans, usually via tick bites. The virus causes tick-borne encephalitis (TBE) in humans, and symptoms range from mild flu-like symptoms to severe and long-lasting sequelae, including permanent brain damage. It has been suggested that within the population of viruses transmitted to the mammalian host, quasispecies with neurotropic properties might become dominant in the host resulting in neurological symptoms. We previously demonstrated the existence of TBEV variants with variable poly(A) tracts within a single blood-fed tick. To characterize the role of the poly(A) tract in TBEV replication and virulence, we generated infectious clones of Torö-2003 with the wild-type (A)3C(A)6 sequence (Torö-6A) or with a modified (A)3C(A)38 sequence (Torö-38A). Torö-38A replicated poorly compared to Torö-6A in cell culture, but Torö-38A was more virulent than Torö-6A in a mouse model of TBE. Next-generation sequencing of TBEV genomes after passaging in cell culture and/or mouse brain revealed mutations in specific genomic regions and the presence of quasispecies that might contribute to the observed differences in virulence. These data suggest a role for quasispecies development within the poly(A) tract as a virulence determinant for TBEV in mice.

  • 49.
    Asghar, Naveed
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Biology. Örebro universitet.
    Petersson, Mona
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Geography.
    Johansson, Magnus
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Biology. Örebro univarsitet.
    Dinnétz, Patrik
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Local land-scape effects on population dynamics of Ixodes ricinus2016In: Geospatial Health, ISSN 1827-1987, Vol. 11, p. 283-289, article id 487Article in journal (Refereed)
  • 50.
    Asghar, Naveed
    et al.
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Biology. Örebro universitet.
    Pettersson, John H-O
    Norwegian Institute of Public Health, Oslo, Norway / Statens veterinärmedicinska anstalt.
    Dinnétz, Patrik
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
    Andreassen, Åshild
    Norwegian Institute of Public Health, Oslo, Norway.
    Johansson, Magnus
    Örebro universitet.
    Deep sequencing analysis of tick-borne encephalitis virus from questing ticks at natural foci reveals similarities between quasispecies pools of the virus2017In: Journal of General Virology, ISSN 0022-1317, E-ISSN 1465-2099, Vol. 98, no 3, p. 413-421Article in journal (Refereed)
    Abstract [en]

    Every year, tick-borne encephalitis virus (TBEV) causes severe central nervous system infection in 10 000 to 15 000 people in Europe and Asia. TBEV is maintained in the environment by an enzootic cycle that requires a tick vector and a vertebrate host, and the adaptation of TBEV to vertebrate and invertebrate environments is essential for TBEV persistence in nature. This adaptation is facilitated by the error-prone nature of the virus's RNA-dependent RNA polymerase, which generates genetically distinct virus variants called quasispecies. TBEV shows a focal geographical distribution pattern where each focus represents a TBEV hotspot. Here, we sequenced and characterized two TBEV genomes, JP-296 and JP-554, from questing Ixodes ricinus ticks at a TBEV focus in central Sweden. Phylogenetic analysis showed geographical clustering among the newly sequenced strains and three previously sequenced Scandinavian strains, Toro-2003, Saringe-2009 and Mandal-2009, which originated from the same ancestor. Among these five Scandinavian TBEV strains, only Mandal-2009 showed a large deletion within the 3' non-coding region (NCR), similar to the highly virulent TBEV strain Hypr. Deep sequencing of JP-296, JP-554 and Mandal-2009 revealed significantly high quasispecies diversity for JP-296 and JP-554, with intact 3' NCRs, compared to the low diversity in Mandal-2009, with a truncated 3' NCR. Single-nucleotide polymorphism analysis showed that 40% of the single-nucleotide polymorphisms were common between quasispecies populations of JP-296 and JP-554, indicating a putative mechanism for how TBEV persists and is maintained within its natural foci.

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